Automotive vehicles include a wide variety of accessories and systems such as headlights, windshield wipers and the like that are controlled by selector switches mounted on the dash or steering column. It is important that selector switches are easy to operate and that they provide the proper "feel". Selector switches must also be durable and robust to provide users with the feeling of quality.
Vehicle manufacturers have set stringent design standards for selector switches. Vehicle manufacturers have also imposed design requirements to assure that customer expectations as to the operation of manual controls are fulfilled.
For example, vehicle light controls must be easy to operate but sufficient turning torque must be required for operation to provide a quality feel. For selector switches that are adjusted by rotating a knob, design requirements are set by vehicle manufacturers to assure that the knob cannot be turned past predetermined arcuate limits. End stops that limit knob movement must be positive and sufficiently durable to resist breakage.
Selector switches for automotive applications have evolved into relatively large complicated structures to meet vehicle manufacturer standards. Different types of selector switches have been developed including switches having rotary switch contacts and switches having sliding switch contacts. One example of a rotary switch is disclosed in U.S. Pat. No. 4,885,434 that discloses a composite push-pull headlight and rotary switch. Typically, a dash-mounted headlight control switch includes multiple functions and may be 3-4 inches in depth. These types of control switches are provided with thick copper contacts that must have the capacity to carry operational circuit current loads. This type of switch is relatively expensive to manufacture and lacks design flexibility.
In an attempt to reduce vehicle cost and weight, vehicle manufacturers have recently begun to utilize multiplexed digital controls for vehicle accessories. In multiplex controls, only digital control level current carrying wiring harnesses are required to connect switches to control circuits. Control circuits are interfaced with operational circuits by relays, SCR or MOSFET interfaces. This can reduce the cost of wiring harnesses by reducing the number and size of wires in wiring harnesses. Control switches can be reduced in size and switch contacts can be designed with lower current-carrying capacity when only control circuit level currents must be carried by the selector switches. Since less current is being controlled by the selector switches, the switches may be designed with reduced heat resistance properties.
Encoders have been developed as standardized electronic components that are used to provide a digital indication of the rotational position of a shaft. Usually, encoders are designed for full rotation and do not include end stops that would prevent rotation in a full circle. Encoders normally are designed to provide only low levels of rotational torque resistance. Encoders also generally provide a large number of digital outputs. For example, a four-bit encoder would generally have sixteen potential outputs, or stops. Few if any automotive systems require as many as sixteen outputs to be controlled by a single switch. The additional potential outputs are unacceptable for automotive accessory controls because the provision of additional no-function stops for a selector switch would be confusing to a automobile operator.
These and other problems in the prior art are addressed by the present invention as summarized below.